1. Field of the Invention
The present invention relates to a technique of avoiding an interference in an operation to be performed by an industrial robot.
2. Description of the Related Art
In a picking operation of picking up a plurality of workpieces stored randomly in a storage box with a robot, it is necessary to control position/orientation of a robot and a tool, i.e. an end effector such as a robot hand, attached to a distal end of the robot so that the hand can hold one objective workpiece in the plurality of workpieces. Position/orientation of workpieces are scattered since these workpieces are stored randomly. Thus, the position/orientation of the tool and the robot arm has to be changed in accordance with position/orientation of the objective workpieces to be picked up, to cause an interference between the tool or the robot and a peripheral object such as the storage box storing the workpieces.
In general, if an interference is found in the teaching operation, the interference can be avoided by modifying the position/orientation of the tool in the teaching operation. However, it is not assured that the interference is avoided in an actual operation in the above picking operation. Thus, it has been necessary to place an objective workpiece to have predetermined position/orientation in every picking operation or prepare an ambience around the workpieces which never cause an interference.
Preparing a complete ambience around the randomly stored workpieces requires laborious work and a long time to be contrary to labor saving and automated operation by a robot.
If a workpiece is placed to have predetermined position/posture, it is possible for an operator to teach a robot so as not to cause an interference through an off-line programming. However, a burden on the operator increases as to how to avoid an interference by teaching the robot appropriate position/orientation of the tool.
The present invention provides an interference avoiding device capable of determining an interference in an robot operation in advance and avoiding the interference. With the interference avoiding device of the present invention, it is unnecessary to prepare a specific ambience around an object of operation of the robot even in a picking operation of randomly stored workpieces, to reduce a burden on an operator.
An interference avoiding device of the present invention comprises: storing means for storing information on shape/dimensions of a operational device attached to a robot, and shape/dimensions and position/orientation of a peripheral object; interference determining means for determining an interference between the operational device and the peripheral object based on the information stored in the storing means and a commanded position/orientation of the operational device; position/orientation setting means for setting a new position/orientation of the operational device for avoiding the interference between the operational device and the peripheral object in place of the commanded position/orientation of the tool, when it is determined that an interference will occur by the interference determining means.
The position/orientation setting means may automatically determine the new position/orientation of the operational device for avoiding the interference. Alternatively, the position/orientation setting means may select one of a plurality of predetermined positions/orientations.
Alternatively, the position/orientation setting means may set a newly taught position/orientation of the operational device for avoiding the interference.
The interference avoiding device may further comprise means for continuously operating the robot in accordance with the new position/orientation of the operational device.
The position/orientation setting means may stop an operation of the robot when it is determined that an interference will occur by the interference determining means.
The interference avoiding device may further comprise determining means for determining an interference between the operational device and the peripheral object on condition of the new position/orientation of the operational device, and display means for displaying a message when it is determined that an interference will occur by the determining means.
The interference avoiding device may further comprise determining means for determining an interference between the operational device and the peripheral object on condition of the new position/orientation of the operational device, and control means for suspending an operation of the robot when it is determined that an interference will occur by the determining means and then resuming the operation of the robot.
The position/orientation setting means may rewrite an operation program of the robot by replacing the commanded position/orientation of the tool with the new position/orientation for avoiding the interference.
The interference determining means may determine an interference between the operational device and the peripheral object in operation of the robot.
The interference avoiding device may be incorporated into a robot controller or an information processing device connected to the robot. The information processing device may include an operation simulation device of the robot.
The new position/orientation of the operational device may be used for obtaining information by means a sensor attached to the robot.
The commanded position/orientation of the operational device may be determined based on information obtained by a sensor attached to the robot. In this case, the storing means may store information on position/orientation of a workpiece in a teaching operation and position/orientation of a tool as the operational device for grasping the workpiece in the teaching operation, and the commanded position/orientation of the tool is determined based on the determined position/orientation of the workpiece and the stored information on the positions/orientations of the workpiece and the tool in the teaching operation. Alternatively, the storing means may store information on position/orientation of a tool as the operational device for holding a workpiece with respect to position/orientation of the workpiece in a teaching operation based on CAD information in an off-line teaching device, and the commanded position/orientation of the tool is determined based on the determined position/orientation of the workpiece and the stored information on the position/orientation of the tool with respect to the position/orientation of the workpiece.
The sensor may comprise a two-dimensional sensor or a three-dimensional sensor.
The operation to be performed by the robot may be a picking operation of picking up a workpiece by the operational device, and the peripheral object is a storage box storing workpieces. Further, the operation to be performed by the robot may be one of spot welding, arc welding and sealing.
The robot may be directly or indirectly fixed to a structure fixed on a floor, a wall or a ceiling, and may be arranged to be movable along one or two axes.